A 43-year-old man visiting the United States from Thailand comes to the emergency department due to 10 days of hemoptysis. He also has had night sweats but reports no fever or weight loss. Temperature is 37.7 C (99.9 F), blood pressure is 118/68 mm Hg, pulse is 86/min, and respirations are 18/min. Physical examination shows right-sided rhonchi and crackles. Chest x-ray shows an infiltrate in the right upper lobe. Sputum samples from 3 consecutive days are also obtained. After 72 hours of tuberculin skin test (TST) placement, there is no induration at the site; however, 2 of 3 sputum sample smears reveal acid-fast bacilli. Which of the following best explains the negative TST in this patient?

Question

A 43-year-old man visiting the United States from Thailand comes to the emergency department due to 10 days of hemoptysis.  He also has had night sweats but reports no fever or weight loss.  Temperature is 37.7 C (99.9 F), blood pressure is 118/68 mm Hg, pulse is 86/min, and respirations are 18/min.  Physical examination shows right-sided rhonchi and crackles.  Chest x-ray shows an infiltrate in the right upper lobe.  Sputum samples from 3 consecutive days are also obtained.  After 72 hours of tuberculin skin test (TST) placement, there is no induration at the site; however, 2 of 3 sputum sample smears reveal acid-fast bacilli.  Which of the following best explains the negative TST in this patient?

Quizplus · Accepted Answer

Eductional Objective: Approximately 25% of patients with active TB have false-negative tuberculin skin testing (TST) (anergy) due to an impaired cell-mediated immune response.  These individuals are at greater risk for severe, disseminated disease and death.  False-negative TST can also be seen with immunocompromise, improper injection technique, and recent infection.

A 43-Year-Old Man Visiting the United States from Thailand Comes